Wireless semiconductor device having low power consumption

ABSTRACT

The invention provides a semiconductor device that power is stabilized by suppressing power consumption as much as possible. The semiconductor device of the invention includes a logic portion and a memory portion each including a plurality of transistors, a detecting portion for detecting one or both of operation frequencies of the logic portion and the memory portion, a Vth control for supplying a Vth control signal to one or both of the logic portion and the memory portion, and an antenna. Each of the plurality of transistors has a first gate electrode which is input with a logic signal, a second gate electrode which is input with the Vth control signal, and a semiconductor film such that the second gate electrode, the semiconductor film, and the first gate electrode are provided in this order from the bottom.

TECHNICAL FIELD

The present invention relates to a semiconductor device capable oftransmitting and receiving data.

BACKGROUND ART

In recent years, a semiconductor device has been developed and used as aCPU and a memory. Among them, a semiconductor device which consumeslarge power has a problem that a larger battery and a cooling fan arerequired, thereby the electronic apparatus itself is increased in size.In view of the foregoing, a composite semiconductor device is suggested,which has a structure where a wiring substrate and a package areattached to each other so as to satisfy high thermal conductivity andlow elasticity.

[Patent Document 1]

-   Japanese Patent Laid-Open No. 07-74282

A semiconductor device capable of transmitting and receiving data hasbeen developed, which is called a wireless tag, an RFID tag, or thelike. The semiconductor device which has been put to practical usecomprises an antenna and a circuit formed using a semiconductorsubstrate (an IC chip) in many cases. The IC chip comprises a pluralityof transistors each of which has a fixed threshold voltage.

DISCLOSURE OF INVENTION

In a wireless tag, power is difficult to be stabilized and powerconsumption is required to be suppressed as much as possible because thepower is supplied from an antenna. In addition, a wireless tag carriesout complex processes such as reading out data from a storage medium anda cryptanalysis. In order to carry out such a complex process as thecryptanalysis, there has been a problem that high power consumption hasbeen required. As the power consumption is increased, strongelectromagnetic waves are required to be input, there has been a problemthat high power consumption of a reader/writer has been needed and otherdevice and the human body have been adversely affected, for example.Furthermore, the communication distance between the wireless tag and thereader/writer has been restricted.

In view of the foregoing, the invention provides a semiconductor devicein which stabilization of power is achieved by suppressing the powerconsumption as much as possible. In addition, the invention provides asemiconductor device in which power is not unstable due to a complexprocess such as a cryptanalysis and stabilization of the power isachieved. Furthermore, the invention provides a semiconductor device inwhich strong electromagnetic waves are not required to be input and thecommunication distance to a reader/writer is improved.

The invention takes the following measures in order to solve theaforementioned problem of conventional art.

A semiconductor device of the invention comprises a logic portion and amemory portion each including a plurality of transistors, a detectingportion for detecting operation frequencies of one or both of the logicportion and the memory portion, a Vth control for supplying a Vthcontrol signal to one or both of the logic portion and the memoryportion, and an antenna. Each of the plurality of transistors has afirst gate electrode which is input with a logic signal, a second gateelectrode which is input with the Vth control signal, and asemiconductor film such that the second gate electrode, thesemiconductor film, and the first gate electrode are provided in thisorder from the bottom.

In addition, a semiconductor device of the invention may comprise asubstrate provided with a plurality of transistors. Alternatively, asemiconductor device of the invention may comprise a substrate providedwith a plurality of transistors and an antenna. Alternatively, asemiconductor device of the invention comprises a substrate providedwith a plurality of transistors and a base provided with an antenna suchthat the substrate and the base may be attached to each other so as toconnect the plurality of transistors to the antenna.

In addition, in a semiconductor device of the invention, a substrate maybe a glass substrate or a flexible substrate. In addition, a logicportion may comprise more than one of a control circuit, an arithmeticcircuit, an input/output circuit, a power source circuit, a clockgenerating circuit, a data demodulation/modulation circuit, and aninterface circuit. In addition, a detecting portion may be a program ora storage medium storing the program.

According to the invention having the above-described constitution, asemiconductor device in which low power consumption is achieved can beprovided. Therefore, such a semiconductor device can be provided thatpower is not unstable due to a complex process such as a cryptanalysisand stable operation is achieved. In addition, such a semiconductordevice can be provided that strong electromagnetic waves are notrequired to be input and the communication distance to a reader/writeris improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating constitution of a semiconductor deviceof the invention.

FIGS. 2A to 2C are diagrams illustrating constitution of a semiconductordevice of the invention.

FIG. 3 is a diagram illustrating constitution of a semiconductor deviceof the invention.

FIGS. 4A and 4B are diagrams illustrating constitution of asemiconductor device of the invention.

FIG. 5 is a diagram illustrating constitution of a semiconductor deviceof the invention.

FIGS. 6A to 6D are illustrating describing constitution of semiconductordevices of the invention.

FIGS. 7A to 7D are diagrams illustrating constitution of a semiconductordevice of the invention.

FIGS. 8A to 8H are views illustrating applications of a semiconductordevice of the invention.

FIGS. 9A and 9B are views illustrating applications of a semiconductordevice of the invention.

FIGS. 10A to 10C are diagrams illustrating constitution of asemiconductor device of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Although the invention will be specifically described by way ofembodiments with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless such changes andmodifications depart from the scope of the invention, they should beconstrued as being included in the invention. Therefore, the inventionshould not be interpreted as being limited to the disclosure of theembodiments. Note that identical portions in constitution of theinvention are denoted by the same reference numerals in differentdrawings.

A semiconductor device 10 of the invention comprises a logic portion 11,a memory portion 12, a detecting portion 13, a Vth control 14, and anantenna 15 (see FIG. 1). The semiconductor device 10 of the inventioncommunicates data in noncontact manner. The logic portion 11 is morethan one of a power source circuit, a clock generating circuit, a datademodulation/modulation circuit, an interface circuit, a controlcircuit, an arithmetic circuit, and an input/output circuit. The controlcircuit, the arithmetic circuit, and the input/output circuit arecomponents of a CPU (Central Processing Unit). The power source circuitfunctions to generate power sources for respective circuits in thesemiconductor device based on alternating signals input from the antenna15. The clock generating circuit functions to generate clocks forrespective circuits in the semiconductor device based on alternatingsignals input from the antenna 15. The data demodulation/modulationcircuit functions to demodulate and modulate data for communicating witha reader/writer 18. The antenna 15 functions to transmit and receive anelectromagnetic field and radio waves. The reader/writer 18 controls thecommunication with the semiconductor device, the control, and theprocessing of data thereof. Note that the logic portion 11 is notlimited to this constitution and can take various constitution. Forexample, another component such as a compensatory circuit of powersource voltage and hardware dedicated to a cryptanalysis is additionallyprovided. The memory portion 12 is one or more of a DRAM (Dynamic RandomAccess Memory), an SRAM (Static Random Access Memory), an FeRAM(Ferroelectric Random Access Memory), a masked ROM (masked Read OnlyMemory), a fuse PROM (fuse Programmable Read Only Memory), an anti-fusePROM, an EPROM (Electrically Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory), a flash memory,and the like.

The logic portion 11 and the memory portion 12 each includes a pluralityof transistors. Each of the transistors has a first gate electrode whichis input with a logic signal and a second gate electrode which is inputwith a Vth control signal. Description below is made on a structure ofthe transistor having the first and second gate electrodes (see FIGS. 2Aand 2B). In the drawings, an n-type transistor 21 and a p-typetransistor 22 are exemplarily shown as the plurality of transistors.

The n-type transistor 21 and the p-type transistor 22 are formed over asubstrate 20 made of glass, quartz, plastic, metal oxide, or silicon.The n-type transistor 21 has a first gate electrode 33, a semiconductorfilm including source and drain regions (also called impurity regions)26 and 27 and a channel forming region 30, and a second gate electrode23. The p-type transistor 22 has a first gate electrode 34, asemiconductor film including source and drain regions 28 and 29 and achannel forming region 31, and a second gate electrode 24. A first gateinsulating film 32 is provided between the first gate electrode 33/34and the semiconductor film. A second gate insulating film 25 is providedbetween the second gate electrode 23/24 and the semiconductor film.Moreover, source and drain wirings 35 to 37 connected to the source anddrain regions 26 to 29 are provided over the substrate 20.

Next, a characteristic between drain current (I_(d)) and gate voltage(V_(g)) of the above-mentioned transistor having the first and secondgate electrodes is described (see FIG. 2C). A curve 91 shows thecharacteristic when the second gate electrode of the transistor isapplied with positive voltage, a curve 92 shows the characteristic whenthe second gate electrode is applied with 0 V, and a curve 93 shows thecharacteristic when the second gate electrode is applied with negativevoltage.

As shown here, when the second gate electrode is applied with positivevoltage, the curve is shifted to the left and the threshold voltagefalls. On the other hand, when the second gate electrode is applied withnegative voltage, the curve is shifted to the right and the thresholdvoltage rises. The invention utilizes this phenomenon such that thesecond gate electrode is applied with positive voltage to lower thethreshold voltage in the case where high-speed operation is required,whereas the second gate electrode is applied with negative voltage toincrease the threshold voltage in the case where power consumption is tobe reduced by reducing leakage current.

The detecting portion 13 comprises an operation-frequency detectingmeans for detecting operation frequencies of the logic portion 11 andthe memory portion 12, and a discriminating means for discriminatingoperation modes of the logic portion 11 and the memory portion 12 (seeFIG. 3). The operation-frequency detecting means counts how many times acertain instruction is used in a certain period. The discriminatingmeans compares an output of the operation-frequency detecting means witha reference value stored in the memory, and the operation mode isrecognized as a first mode (a standby mode) if the output of theoperation-frequency detecting means is equal to or smaller than thereference value. On the other hand, if the output of theoperation-frequency detecting means is equal to or larger than thereference value, the operation mode is recognized as a second mode (anactive mode). The detecting portion 13 is a program or a storage mediumstoring the program. Note that the memory for storing the referencevalue can be provided inside or outside the semiconductor device.

The Vth control 14 comprises a memory 63, a D/A converter portion 64,and a buffer 65 (see FIG. 3). The memory 63 receives data on a detectionresult from the detecting portion 13 to store it. The D/A converterportion 64 converts the stored data into analog voltage. The buffer 65outputs the analog voltage after buffering and outputs a Vth controlsignal. Here, a Vth control signal for making threshold voltage high isoutput to a transistor in a block of the logic portion 11 and the memoryportion 12 in a standby mode, whereas a Vth control signal for makingthreshold voltage low is output to a transistor in a block of the logicportion 11 and the memory portion 12 in an active mode. By beingsupplied with the Vth control signal for setting high threshold voltage,the transistor of the block in a standby mode surely turns OFF.Consequently, leakage current is reduced and low power consumption isachieved. On the other hand, by being supplied with the Vth controlsignal for setting low threshold voltage, high-speed operation of thetransistor of the block in an active mode is achieved.

Note that a Vth control signal is supplied to both of the blocks in astandby mode and in an active mode herein, however, the invention is notlimited to this and the Vth control signal may be supplied to eitherblock in a standby mode or in an active mode. Constitution of the Vthcontrol 14 is not limited to the above constitution. For example, in thecase where the logic portion 11 and the memory portion 12 have aplurality of blocks, the memory 63, the D/A converter portion 64, andthe buffer 65 may be provided per the block.

A non-contact type semiconductor device is described hereabove, however,the invention is not limited to this and may be a contact type.

EMBODIMENT 1

Constitution of the operation-frequency detecting means and thediscriminating means in the detecting portion 13 is described usingFIGS. 4A and 4B. The operation-frequency detecting means includes anaddress comparator 71, an address memory 72, a counter 73, and a resetsignal generating circuit 74. The discriminating means includes adiscriminating circuit 75 and a discriminating reference data memory 76.

The address comparator 71 is connected to an address bus 70 and theaddress memory 72. First address data is input from the address bus 70.The first address data and second address data which is input to theaddress memory 72 are compared with each other by the address comparator71. When the first address data and the second address data agree witheach other, a signal showing the agreement is output to the counter 73.The counter 73 counts an output of the address comparator 71. The resetsignal generating circuit 74 outputs a reset signal periodically to thecounter 73.

In the case where one reset signal is input to the counter 73 per 0.01seconds, for example, the counter 73 counts how many times the firstaddress data and second address data agree with each other for 0.01seconds.

Note that a known counter having a reset terminal can be used as thecounter 73. The reset signal generating circuit 74 divides a fixedfrequency signal such as a clock signal into the required number.

The discriminating circuit 75 compares an output of the counter 73 witha reference value stored in the discriminating reference data memory 76.In the case where the output of the counter 73 is equal to or largerthan the reference value, the Vth control 14 is operated to supply a Vthcontrol signal for making threshold voltage low. Meanwhile, in the casewhere the output of the counter 73 is equal to or smaller than thereference value, the Vth control 14 is operated to supply a Vth controlsignal for making threshold voltage high. Specifically, a referencevalue in the discriminating reference data memory 76 is subtracted froman output of the counter 73. The Vth control 14 is operated when thedifference becomes 0 from a positive value or when the differencebecomes 0 from a negative value. In addition, the Vth control 14 isoperated when the difference becomes a negative value from 0 or when thedifference becomes a positive value from 0.

When a reference value stored in the discriminating reference datamemory 76 is subtracted from an output of the counter 73, and thedifference becomes 0 from a positive value or when the differencebecomes 0 from a negative value, the Vth control 14 supplies a Vthcontrol signal for making the threshold voltage low, a Vth controlsignal for making the threshold voltage high, or no Vth control signal.

When the difference becomes a negative value from 0, the Vth control 14supplies a Vth control signal for making the threshold voltage high.

Meanwhile, when the difference becomes a positive value from 0, the Vthcontrol 14 supplies a Vth control signal for making the thresholdvoltage low.

A constitution of the address comparator 71 is described next. The caseof a 4-bit is illustrated here for simplicity. Address data of each bitof the address bus 70 and the address memory 72 is input to each ofinput nodes of EXOR circuits 77 to 80. Outputs of the EXOR circuits 77to 80 are input to input nodes of an NOR circuit 81. An output node ofthe NOR circuit 81 is connected to a latch circuit 82. A latch pulse isinput to the latch circuit 82 to latch data after ON/OFF switching isterminated. Note that the latch circuit 82 is provided for preventing aglitch in switching the operation and is not necessarily provided.

EMBODIMENT 2

Constitution of the logic portion 11, which is one of theabove-mentioned five components of the invention (the logic portion 11,the memory portion 12, the detecting portion 13, the Vth control 14, andthe antenna 15), is described in detail using FIG. 5. A semiconductordevice corresponding to a CPU is illustrated for description here.

The semiconductor device corresponding to a CPU comprises a timingcontrol 51, an instruction decoder 52, a register array 53, an addresslogic and buffer 54, a data bus interface 55, an ALU (Arithmetic LogicUnit) 56, an instruction register 57, the detecting portion 13, and theVth control 14. The timing control 51, for example, receives aninstruction from the outside and converts it into data for the inside totransmit to another block, and provides an instruction of reading orwriting of memory data, or the like to the outside depending on theinside operation. The instruction decoder 52 converts an outsideinstruction into an instruction for the inside. The register array 53 isa volatile memory to temporarily hold data. The address logic and buffer54 specifies an address of an external memory. The data bus interface55, for example, provides data to an external memory and the like, andreads data of the external memory. The ALU 56 performs an arithmeticoperation. The instruction register 57 temporarily stores data.

The logic portion 11 corresponds to the timing control 51, theinstruction decoder 52, the register array 53, the address logic andbuffer 54, the data bus interface 55, the ALU 56, and the instructionregister 57. The detecting portion 13 is connected to each of thecircuits included in the logic portion, 11 and to the Vth control 14.The Vth control 14 is connected to each of the circuits in the logicportion 11 and to the detecting portion 13.

EMBODIMENT 3

According to a semiconductor device of the invention, data reading anddata writing can be performed in a noncontact manner, and any one ofdata transmission methods can be employed which are generally classifiedinto three methods, that is, an electromagnetic coupling method by whichdata communication is performed by mutual induction by a couple of coilsbeing provided so as to face each other, an electromagnetic inductionmethod by which data communication is performed by an inductionelectromagnetic field, and a radio wave method by which datacommunication is performed by utilizing radio waves. The antenna 15 fortransmitting data is provided in two manners, that is, the case wherethe antenna 15 is provided over the substrate 20 having a plurality oftransistors (see FIGS. 6A and 6C), and the case where a terminal portionis provided over the substrate 20 having a plurality of transistors andthe antenna 15 is provided to connect to the terminal portion (see FIGS.6B and 6D). The plurality of transistors provided over the substrate 20is called an element group 85 herein.

In the former structure (FIGS. 6A and 6C), the element group 85constituting the logic portion 11 and the like, and a conductive filmfunctioning as the antenna 15 are provided over the substrate 20. In thedrawings, the conductive film functioning as the antenna 15 is providedin the same layer as that of source and drain wirings. However, theinvention is not limited to this structure. It is possible to providethe antenna 15 in the same layer as that of the first gate electrode orthe second gate electrode, or to cover the element group 85 with aninsulating film and provide the antenna 15 over the insulating film.

In the latter structure (FIGS. 6B and 6D), the element group 85 and aterminal portion 86 are provided over the substrate 20. In the drawings,a source or drain wiring of transistors included in the element group 85is used as the terminal portion 86. Moreover, the substrate 20 isattached to a substrate (a base) 84 such that the terminal portion 86and the antenna 15 are connected to each other. Conductive particles 87and resins 88 are interposed between the substrate 20 and the substrate84.

The element group 85 can be provided at low cost by forming a pluralityof the element groups 85 over a large substrate and then separating fromone another. A quartz substrate, a glass substrate, and the like can beemployed as the substrate, and preferably the glass substrate which hasno restriction on size is employed.

The plurality of transistors included in the element group 85 may beprovided in a plurality of layers. When forming the element group 85 ina plurality of layers, an interlayer insulating film is used, which ispreferably formed of a resin material such as epoxy resin or acrylicresin, a transmissive resin material such as polyimide resin, a compoundmaterial produced by polymerization such as siloxane polymer, a materialcontaining water-soluble homopolymer and water-soluble copolymer, or aninorganic material.

A siloxane compound material has a bond of silicon and oxygen as abackbone structure and contains hydrogen as a substituent or furthercontains at least one of fluorine, an alkyl group, and aromatichydrocarbon as a substituent. Furthermore, as a material for theinterlayer insulating film, a low permittivity (low-k) material ispreferably employed in order to reduce parasitic capacitance betweenlayers. When the parasitic capacitance is reduced, high-speed operationand low power consumption can be achieved.

As an active layer of each of the transistors in the element group 85,any one of an amorphous semiconductor, a microcrystalline semiconductor,a polycrystalline semiconductor, an organic semiconductor can beemployed, though in particular, an active layer crystallized using ametal element as a catalyst or an active layer crystallized by laserirradiation is preferably used in order to obtain a transistor having agood property. Furthermore, a semiconductor layer formed by plasma CVDusing an SiH₄/F₂ gas or an SiH₄/H₂ gas, or a layer obtained byirradiating laser to the semiconductor layer may be preferably used asthe active layer.

For the plurality of transistors in the element group 85, a crystallinesemiconductor layer crystallized at a temperature of 200 to 600° C.(preferably 350 to 500° C.) (a low-temperature polysilicon layer) or acrystalline semiconductor layer crystallized at a temperature of 600° C.or more (a high-temperature polysilicon layer) can be employed. Notethat in the case where a high-temperature polysilicon layer is to beformed over a substrate, a quartz substrate can be employed as well as aglass substrate.

It is desirable that hydrogen or halogen be added to an active layer(particularly, a channel forming region) of each of the transistors inthe element group 85 at a concentration of 1×10¹⁹ to 1×10²² atoms/cm³,and more preferably 1×10¹⁹ to 5×10²⁰ atoms/cm³. According to this, anactive layer with few defects, where few cracks are generated, can beobtained.

In addition, a barrier film for preventing a contaminant such as analkaline metal is preferably provided so as to cover the transistors inthe element group 85 or the element group 85 itself. According to this,such element group 85 that is free from contamination and has improvedreliability can be obtained. Note that the barrier film may be formedwith a silicon nitride film, a silicon nitride oxide film, a siliconoxynitride film, or the like.

The thickness of the active layer of the transistor in the element group85 is 20 to 200 nm, preferably 40 to 170 nm, more preferably 45 to 55 nmor 145 to 155 nm, and still more preferably 50 nm or 150 nm. Accordingto this, the element group 85 where few cracks are generated even whenit is bent can be obtained.

Furthermore, crystals constituting the active layer of the transistor inthe element group 85 are preferably formed such that the crystal grainboundary thereof extends parallel to the flowing direction of carriers(the channel length direction). Such an active layer can be formed usinga continuous wave laser (CWLC) or a pulsed laser operating at afrequency of 10 MHz or more, and preferably 60 to 100 MHz.

The transistor in the element group 85 preferably has an S value(subthreshold value) of 0.35 V/sec or less (preferably, 0.09 to 0.25V/sec) and a mobility of 10 cm²/Vs or more. Such properties can beachieved by forming the active layer using a continuous wave laser or apulsed laser operating at a frequency of 10 MHz or more.

Further, the element group 85 has a frequency of 1 MHz or more, andpreferably 10 MHz or more at the ring oscillator level (at a voltage of3 to 5 V). Alternatively, the property of frequency thereof per gate is100 kHz or more, and preferably 1 MHz or more (at a voltage of 3 to 5V).

The element group 85 is formed over the substrate 20 formed of glass,quartz or the like. The element group 85 over the substrate 20 may beused as it is, or may be peeled off from the substrate 20 (see FIG. 7A)and then attached to a flexible substrate 59 (see FIG. 7B) in order toadd further value. As the flexible substrate 20, a plastic substratesuch as polycarbonate, polyarylate, polyether sulfone and apolytetrafluoroethylene substrate, a ceramic substrate or the like canbe employed.

The element group 85 can be peeled off from the substrate 20 by a methodof removing a peel-off layer provided between the substrate 20 and theelement group 85 by an etchant, or by a method of removing the peel-offlayer partially by an etchant and then physically peeling off theelement group. 85 from the substrate 20. Note that the physical peelingis to peel by a stress applied externally, for example, a stress due togas pressure by gas sprayed from a nozzle or ultrasonic waves.

Alternatively, the element group 85 may be peeled off from the substrate20 by (1) a method such that a metal oxide film is formed between thehigh heat-resistant substrate 20 and the element group 85, and the metaloxide film is weakened by crystallization, thereby peeling off theelement group 85; (2) a method such that an amorphous silicon filmcontaining hydrogen is formed between the high heat-resistant substrate20 and the element group 85, and the amorphous silicon film is removedby laser irradiation or etching, thereby peeling off the element group85; (3) a method such that the high heat-resistant substrate 20 overwhich the element group 85 is formed is removed mechanically or byetching using a solution or a gas such as ClF₃, ClF₂, ClF, or BrF₃,thereby peeling the element group 85; or the like. The peeled elementgroup 85 can be attached to the substrate 59 with a commercial adhesivesuch as an epoxy resin adhesive or a resin additive.

As set forth above, by attaching the element group 85 to the secondsubstrate 59, which is flexible, a thin, light and highlyimpact-resistant semiconductor device can be provided (see FIG. 7C).Further, the flexibility enables to attach the semiconductor device to acurved surface or an irregular shaped surface, leading to variousapplications. For example, a wireless tag 61 that is one mode of thesemiconductor device of the invention can be attached close to a curvedsurface such as a medicine bottle (see FIG. 7D). If the substrate 20 isreused, cost for the semiconductor device can be reduced. In addition,the flexible substrate 59 is inexpensive as compared with the substrate20, thereby reducing the cost for the semiconductor device. Thisembodiment can be implemented in free combination with theaforementioned embodiment mode and embodiments.

EMBODIMENT 4

In this embodiment, a flexible wireless tag formed by a peeling processis described (see FIG. 10A). The wireless tag includes a flexibleprotective layer 2301, a flexible protective layer 2303 having anantenna 2304, and an element group 2302 formed by a peeling process. Theantenna 2304 formed over the protective layer 2303 is electricallyconnected to the element group 2302. Although the antenna 2304 is formedonly over the protective layer 2303 in the drawing, the invention is notlimited to this and the antenna 2304 may be additionally formed adjacentto the protective layer 2301. Note that a barrier film is preferablyformed between the element group 2302 and the protective layers 2301 and2303 using a silicon nitride film or the like. According to this, awireless tag having high reliability can be provided so as not tocontaminate the element group 2303.

The antenna 2304 is desirably formed of silver, copper, or metal coatedwith them. The antenna 2304 and the element group 2302 are connected toeach other by UV treatment or ultrasonic treatment using an anisotropicconductive film, though the invention is not limited to this connectingmethod and various methods can be adopted.

The element group 2302 sandwiched between the protective layers 2301 and2303 may have a thickness of 5 μm or less, and preferably a thickness of0.1 to 3 μm (see FIG. 10B showing a cross sectional structure). When thetotal thickness of the protective layers 2301 and 2303 is d, thethickness each of the protective layers 2301 and 2303 is preferably setto be (d/2)±30 μm, and more preferably (d/2)±10 μm. It is desirable thatthe protective layers 2301 and 2303 each have a thickness of 10 to 200μm The area of the element group 2302 is 5 mm square (25 mm²) or less,and preferably 0.3 to 4 mm square (0.09 to 16 mm²).

The protective layers 2301 and 2303, which are formed of an organicresin material, have a property of being resistant to bending. Theelement group 2302 itself formed by a peeling process is also resistantto bending as compared with a single crystalline semiconductor. Theelement group 2302 can be attached close to the protective layers 2301and 2303 without any space therebetween, thereby a completed wirelesstag itself can have a structure resistant to bending. Such element group2302 sandwiched between the protective layers 2301 and 2303 may bedisposed on a surface of or inside an object, or mounted inside a pieceof paper.

Described next is the case of attaching the element group formed by apeeling process to a substrate having a curved surface (see FIG. 10C).One transistor selected from the element group formed by a peelingprocess is illustrated in FIG. 10C. This transistor is formed linearlyin the direction of current flowing. In other words, a drain electrode2305, a gate electrode 2307 and a source electrode 2306 are arrangedlinearly. In addition, the direction of an arc drawn by the substrate isperpendicular to that of current flowing. According to such a structure,it is possible to reduce the effect of stress and suppress variations incharacteristics of transistors included in the element group even whenthe substrate is bent to draw an arc.

Further, in order to prevent an active element such as a transistor frombeing damaged by stress, it is desirable that an active region (asilicon island portion) of the active element occupy 5 to 50%(preferably, 5 to 30%) of the whole area of the substrate. In a regionwhere no active element such as a TFT is provided, a base insulatingfilm material, an interlayer insulating film material and a wiringmaterial are mainly provided. A region other than the active region of atransistor and the like preferably occupies 60% or more of the wholearea of the substrate. According to such a structure, a highlyintegrated semiconductor device and easily bendable can be provided.

A semiconductor device of the invention can be applied to variousfields. A wireless tag that is one mode of the semiconductor device ofthe invention, for example, can be mounted on bills, coins, securities,certificates, bearer bonds, packing containers, books, a recordingmedium, personal items, vehicles, food items, clothing, healthcareitems, livingwares, medicals, an electronic apparatus, and the like. Thebills and the coins mean currency in the market and include a note thatis a currency in a specific area (a cash voucher), memorial coins andthe like. The securities mean a check, a stock certificate, a promissorynote, and the like (see FIG. 8A). The certificates mean a driver'slicense, a resident card and the like (see FIG. 8B). The bearer bondsmean a stamp, various gift coupons and the like (see FIG. 8C). Thepacking containers mean a wrapping paper for a lunch box or the like, aplastic bottle and the like (see FIG. 8D). The books mean a book, avolume and the like (see FIG. 8E). The recording medium means DVDsoftware, a video tape and the like (see FIG. 8F). The personal itemsmean a bag, glasses and the like (see FIG. 8G). The vehicles mean awheeled vehicle such as a bicycle, a vessel and the like (see FIG. 8H).The food items mean foods, beverages and the like. The clothing meanwear, footwear and the like. The healthcare items mean medical devices,health appliances and the like. The livingwares mean furniture, alighting apparatus and the like. The medicals mean medicines,agricultural chemicals and the like. The electronic apparatus means aliquid crystal display device, an EL display device, a TV receiver (a TVset, a television device, and a thin television device), a mobile phone,and the like. When a wireless tag is mounted on the bills, the coins,the securities, the certificates, the bearer bonds, and the like,counterfeiting thereof can be prevented. When a wireless tag is mountedon the packing containers, the books, the recording medium, the personalitems, the food items, the livingwares, the electronic apparatus, andthe like, the efficiency of the inspection system, the rental system andthe like can be improved. When a wireless tag is mounted on thevehicles, the healthcare items, the medicals and the like,counterfeiting and theft thereof can be prevented and the medicines canbe prevented from being taken in the wrong manner. The wireless tag maybe attached to a surface of a product or mounted inside a product. Forexample, the wireless tag may be mounted inside a page of a book, ormounted inside an organic resin of a package.

When the invention is thus applied to product management or distributionsystem, high performance system can be achieved. For example, areader/writer 95 is provided on the side of a portable terminalincluding a display portion 94 while a wireless tag 96 that is one modeof the semiconductor device of the invention is provided on the side ofa product 97 (see FIG. 9A). In this case, when the wireless tag 96 isput close to the reader/writer 95, the display portion 94 displays dataon the product 97 such as ingredients, a place of origin, and a recordof the distribution process. Conventionally, the data on the product 97is limited to the one shown on a label. Meanwhile, a larger amount ofdata can be obtained by providing the wireless tag 96. As anotherexample, the reader/writer 95 can be provided beside a conveyor belt(see FIG. 9B). In such a case, the product 97 can be inspected easily.This embodiment can be implemented in free combination with theaforementioned embodiment mode and embodiments.

1. A semiconductor device comprising: a logic portion; a memory portion;a detecting portion for detecting at least one of an operation frequencyof the logic portion and an operation frequency of the memory portion; aVth control for supplying a Vth control signal to at least one of thelogic portion and the memory portion depending on a detection resultfrom the detecting portion; and an antenna, wherein each of the logicportion and the memory portion comprises at least one transistor;wherein the at least one transistor has a first gate electrode which isinput with a logic signal and a second gate electrode which is inputwith the Vth control signal, and wherein at least the logic portion isprovided with electric power from the antenna.
 2. A semiconductor devicecomprising: a logic portion; a memory portion; a detecting portion fordetecting at least one of an operation frequency of the logic portionand an operation frequency of the memory portion; a Vth control forsupplying a Vth control signal to at least one of the logic portion andthe memory portion depending on a detection result from the detectingportion; and an antenna, wherein each of the logic portion and thememory portion comprises at least one transistor, wherein the at leastone transistor has a first gate electrode which is input with a logicsignal, a second gate electrode which is input with the Vth controlsignal, and a semiconductor film, wherein the semiconductor film isprovided over the second gate electrode, wherein the first gateelectrode is provided over the semiconductor film, and wherein at leastthe logic portion is provided with electric power from the antenna.
 3. Asemiconductor device according to any one of claims 1 and 2, wherein thelogic portion comprises more than one of a control circuit, anarithmetic circuit, an input/output circuit, a power source circuit, aclock generating circuit, a data demodulation/modulation circuit, and aninterface circuit.
 4. A semiconductor device according to any one ofclaims 1 and 2, wherein the logic portion comprises a timing control, aninstruction decoder, a register array, an address logic and buffer, adata bus interface, an ALU (Arithmetic Logic Unit), and an instructionregister.
 5. A semiconductor device according to any one of claims 1 and2, wherein the memory portion comprises one or more of a DRAM, an SRAM,an FeRAM, a masked ROM, a fuse PROM, an anti-fuse PROM, EPROM, anEEPROM, and a flash memory.
 6. A semiconductor device according to anyone of claims 1 and 2, wherein the detecting portion is a program or astorage medium storing the program.
 7. A semiconductor device accordingto any one of claims 1 or 2, wherein the at least one transistor isprovided over a substrate.
 8. A semiconductor device according to anyone of claims 1 and 2, wherein the at least one transistor and theantenna are provided over a substrate.
 9. A semiconductor deviceaccording to any one of claims 1 and 2, further comprising a firstsubstrate and a second substrate, wherein the at least one transistor isprovided adjacent to the first substrate, wherein the antenna isprovided adjacent to the second substrate, and wherein the firstsubstrate and the second substrate are attached such that the at leastone transistor and the antenna are electrically connected to each other.10. A semiconductor device according to claim 7, wherein the substrateis one of a glass substrate and a flexible substrate.
 11. Asemiconductor device according to claim 8, wherein the substrate is oneof a glass substrate and a flexible substrate.
 12. A semiconductordevice according to claim 9, wherein each of the first and secondsubstrates is one of a glass substrate and a flexible substrate.